Microbial biomass has been utilized for various applications, such as sources of high energy-content fuels, human and/or animal food, and as chemical precursors. Their lipid components are being validated as renewable, sustainable sources of commodity chemical feedstocks. Other components, such as proteins and carbohydrates, can also serve as attractive resources for food supplements. For example, microbial proteins have been useful sources for protein supplements in rations for terrestrial and companion animals, and in diets for aquatic animals. In addition, microbial carbohydrates are excellent sources of industrial compounds as well as feedstock for fermentation systems.
Currently, organic solvents such as hexane are used to extract lipids from the biomass. One disadvantage is that this technique renders the remaining components unusable for further applications such as feed, fermentation or co-firing, unless additional processing such as steam stripping is used to remove the solvent. However, such additional processing has not been widely practiced in commercial production of microbial biomass, for example, for production of polyunsaturated fatty acids (PUFAs); rather, the delipidated biomass is discarded.
Another disadvantage for extraction of lipids using organic solvents is that the extracted lipids need to be further processed, otherwise they may be unusable for subsequent applications. For example, for use of hexane-extracted lipids for biofuels, the extract requires degumming and removal of pigments as well as significant hydrogenation to yield saturated lipids from the polyunsaturated hydrocarbons.
Therefore, a need exists in the field for technologies and methods, which are not only capable of effectively removing lipids from the biomass, but also retaining valuable residual compositions. Further, a need exists for methods that selectively remove lipids from the biomass, thereby avoiding additional processing steps associated with subsequent use of lipids such as for biofuels.